Fireplace structure and damper



Feb. 23, 1943. A. P. ROBINSON 2,312,006

FIREPLACE STRUCTURE AND DAMPER Filed Jab. 16, 1940 2 Sheets-Sheet 1 Fig. 4

I Zhwentor Alberf P. Robinson Patented Feb. 23, 1943 UNITED STATES ATENT OFFICE FIREPLACE STRUCTURE AND DAMPER Albert P. Robinson, near Seattle, Wash.

Application January 16, 1940, Serial No. 314,062

8 Claims.

My invention relates to fireplace construction, and to fireplace dampers. Such dampers are useful primarily to close the throat of the fireplace against escape upward of warm air from the room, when there is no fire in the fireplace, and to prevent downflow of cold air through the flue into the room. They are sometimes useful to vary the area of the throat opening, thereby to vary or control in some degree the intensity of the fire in the fireplace, but their principal usefulness is, as has been indicated, to close the fireplace throat when the fire is extinguished.

In the usual fireplace construction a wide throat (from side to side), but a comparatively shallow one (from front to rear) is located immediately above the entire width of the combustion space, and converges upwardly and rearwardly, as viewed from the front, to the more nearly square flue. It is generally understood that there is not, and can not be, any down-draft of cold air when hot gas from a fire is rising through the throat opening and flue. Such down-drafts, I have found, do occur. The hot gas, if undisturbed, tends to take the most direct path in rising, which is through the center of the throat and up the center of the flue. If the flue is too large, as it is frequently, the corners of the flue are but little affected by the up-draft, or by the heat thereof, and cold air in these corners, or tending to settle within the flue, or driven or drawn into the flue by wind or draft conditions, tends to fall to the bottom of the flue. There it spreads along the corners of the downwardly -di verging throat, and finally spills into the fireplace at the ends of the throat opening, or, in some installations at only one end, or even at intermediate points.

Such down-drafts occur in all fireplaces to some extent or under some conditions; they are particularly noticeable if the room is tightly closed, since air for combustion is then supplied by such down-drafts. Being not sharply segregated from the upflowing hot gas, such down-drafts tend to mingle therewith and. to cause eddies and interference. The down-draft entrains some of the hot gas and smoke, with the result that the fireplace is said to smoke. Frequently, in attempting to avoid smoking, believed to be due to an insufficiently large flue, the flue is made larger than usual, but the smoking, rather than being prevented, is made worse thereby, the reason being that there is greater space left for the cold interfering down-drafts. As noted above, these downdrafts are particularly noticeable, due to smoking of the fireplace, when the room is tightly closed,

simply because such down-drafts serve as a principal source of air for maintaining combustion. That this is so is evidenced by the fact that such smoking can frequently be relieved or avoided by opening an outside door into such a room, thereby affording a more convenient supply of fresh air than the down-drafts, namely, through the door. This, of course, is scarcely practicable if the fireplace is intended to heat the room to any degree, since the open door admits cold outside air, and chills the room, and it is therefore necessary to accept the down-draft as a necessary evil, or to provide means whereby the objectionable smoking can be avoided in such cases.

It is a principal object of this invention to provide a construction of fireplace which, while permitting down-drafts through the flue and throat into the fireplace itself, will by segregation of the down-draft from the upflowing hot gas, prevent undue intermingling and interference between the two, and will thereby prevent smoking.

It is also an object to provide a fireplace structure having the capabilities indicated, and capable also of employing a fireplace damper which may be adjusted to various positions to close entirely or to regulate the effective size of the throat opening.

More specifically, and with particular reference to the last named object, it is a further object to provide a damper having the capability of segregating the cold down-draft from the hot up-draft, and. which includes not only a movable damper plate but a hingedly mounted cover, which cover is ordinarily moved simultaneously with or by the movement of the damper plate, cooperating with the latter to determine the effective size of the throat opening, but which may also, at will, be moved independently of the damper plate, for instance to clean out the space above the fireplace damper.

Also, more specifically, and with particular relation to the first-named object, it is an object to provide a fireplace of simple construction, including a rear wall which has a central upstanding part over which the hot gas passes, and an omitted part at one or both ends, defining a lower lying cold air passage, which passages may both be closed by an upright, preferably swingably mounted damper plate, swingable about an axis adjacent the upper edge of the rear wall, whereby, as it is so swung, the central hot gas passage opens at one side of and above the damper plate, and the down-draft occurs at the ends only of the damper, and is segregated by downwardly directed portions of the damper plate from the upflowing hot gas.

Likewise it is an object to construct the throat in such manner that down-drafts or down blasts, which can scarcely be prevented, are blocked in such manner that they are not likely to blow soot and ashes from the flue into the room, nor to blow directly upon ashes lying upon the hearth, to scatter them into the room, while yet permitting the cold air to spill into the fireplace in a controlled manner, and without interference with the up-draft. In other words, it is not my intention to prevent or avoid down-drafts or down blasts, but so to control them when they do occur that no undesirable results arise therefrom.

Furthermore, and in conjunction with the use of a damper plate, it is an object so to form the H latter that all air moving downwardly through the throat opening is deflected downwardly and to the rear of the combustion space, and is positively baflled and prevented from blowing outwardly into the room.

These and other objects, as will appear hereafter, will be best understood as this specification progresses. The invention, in forms which are at present preferred by me, is shown in the accompanying drawings, described in the specification, and the novel principles thereof will be more particularly defined by the claims which terminate this specification.

Figure 1 is a side-to-side vertical section through the damper, substantially on the line |--l of Figure 4.

Figure 2 is a view similar to Figure 1, illustrating, however, the opposite end of the damper, being a section on the line 2-2 of Figure 3, showing parts in the open position.

Figure 3 is a front-to-rear vertical section through the damper, taken substantially on the line 33 of Figure 2, and Figure 4 is a similar view, on line 44 of Figure 1, showing parts in the closed. position.

Figure 5 is a view similar to Figures .3 and 4,

showing parts in closed position, but illustrating a modified form of damper.

Figure 6 is an isometric view, broken away, of the latter form of damper, built into a fireplace construction, and in use.

The broad principle of my invention, namely, the segregation of the up-draft from the downdraft, may be embodied in various widely different forms of fireplace construction, and, if a damper is used, with various widely different forms of damper, and therefore, as to this principle, I do not desire to be limited to any specific form, and the forms illustrated are chosen merely for purposes of making clear these principles, and because for other reasons they are preferred forms of damper. Likewise the segregation of the up-draft and the down-draft may be accomplished in various ways. The segregation may be accomplished by maintaining these opposed drafts at different levels, as is shown herein, or by concentrating them and maintaining them at different points across the fireplace throat, as is also shown herein, and these two means of segregation may be employed alone, or jointly as shown herein. Other means of segregation may also be employed, as will appear later. Likewise, while it will appear hereafter that the passage for the downflowing cold air is open simultaneously with the passage for the upflowing hot gas, that is not essential to the employment of the invention, though desirable. It is therefore possible to employ quite separate and independent means for controllin the cold air passage and the hot gas passage, respectively, although it is simpler, and therefore preferable, to employ a single means to effect the control of both simultaneously.

Figures 1 to 4 illustrate a damper which, by

reason of its inclusion of a hingedly mounted cover, as well as a hingedly mounted damper plate, is well adapted to varying the effective area of the throat opening, and likewise to carry out the principle of segregation of the drafts. Such a damper as a whole comprises a frame 2 of suitable shape and size. It is not essential that the frame I per se define a complete and closed throat opening, for the frame and the damper may cooperate with elements of the masonry construction M to define such a throat opening, but as shown herein the frame I is formed of the end walls II. the front wall l3, and the more or less upright rear wall l2, all cooperating to define a throat opening. The rear wall- 12 is of particular importance, as will shortly appear. Such a frame is formed with the usual lintel flange M and supporting flanges 15.

In the particular form of damper illustrated in Figures 1 to 4 there is likewise a cover 2, 'hingedly mounted in the frame at 21 upon a transverse axis adjacent its own forward edge, and adjacent the upper edge of the front wall E3 of the frame. The rear edge of the cover 2 is supported in a manner which will presently appear, and this construction enables the cover to be swung upwardly whenever necessary to clean out the space above it, and any debris or soot which may have collected on top of the cover is thus spilled down through, the frame, and the flue immediately above the cover is readily accessible, so that the flue may be readily cleaned, when necessary.

The rear wall l2 projects upwardly spaced somewhat in front of the brickwork B which defines the rear'face of the flue, so that a pocket P is left at the bottom of the flue, wherein cold or relatively cooler air tends to settle. This, rear wall I2 does not extend to the full height of the rear edge of the end walls H. Rather, as is best seen in Figures 1 and 3, a part only, such as the central portion of the rear wall l2, extends upward part way to the top of the rear edge of the end walls, thus defining the pocket P, but a gap is left between the upper edge of theupstanding rear wall [2 and the closed position of the rear edge of the cover '2, which space constitutes part of the throat opening, but this particular part may be designated the hot gas passage, for it is through this cen-' tral portion of the throat opening that the hot gases, as they follow the most direct path, normally pass upwardly: and overthe top of the rear wall l2.

Likewise therea'r wall I2, at one end at least, and preferably at both ends, does not extend to a junction with the end wail, but terminates short thereof, and thus there is left between the end of the rearwall l2 and the adjacent end wall H of the frame a passage C which lies appreciably lower than'theh'ot gas passage H, previously mentioned, and the two are likewise spaced transversely across the width of the throat.

It will now be clear that since the cold air passages C admit to the pocket P, and since these ously the cold air flowing down the corners of the flue, or tending to settle in the pocket P, will be contained by the rear wall I2, but will spill out through the low-lying passages C into the fireplace. Likewise, the hot gas and smoke, which naturally tends to rise through the center of the throat and flue, passes upwardly over the higher rear wall I2 and out at the passage H, avoiding the passages C. If the two passages were at the same level, or if they were not spaced across the throat, interference would result. By proper relative positioning, as to level and as to spacing crosswise, there is accomplished segregation of the hot gas and counterfiowing cold air, by the natural gravity separation of two gases of different thermal densities. Since the two gases are separated, no appreciable interference occurs between their principal currents, and there is nothingsuch as interfering counterfiows and eddies-to drive the smoke back and into the room.

If it should happen that the hot gas flows upwardly through passages C, no great harm would result, for if there is sufficient up-draft at C, there can scarcely be a down-draft there; if there is a down-draft anywhere, it will be here; and if there is no down-draft there are no undesirable results. 7

These separations of level and of spacing or positioning may be sufficient (either or both) in and of themselves to prevent, to the desired or necessary degree, interference between the downflowing cold air and the upfiowing hot gas, and thus, without more, to achieve the principal advantages of this invention. Preferably, however, they are additionally segregated, and preferably such segregation is effected, and other desirable results are accomplished, by the use of a damper plate, as will shortly appear.

So far as the segregation of counterfiowing currents is concerned, no damper plate is necessary, but since it is desirable to be able to close the damper completely, at times when there is no fire in the fireplace, or to close it part-way for certain draft or wind conditions, the throat opening, thus made up of the passages C and H, is arranged to be closed by a damper plate 3, which is shaped complementally to the throat opening, to close the latter. Preferably this damper plate is hingedly mounted'in the frame I upon a transverse horizontal axis defined by the trunnions 3!] and their supporting bearings, this axis being located adjacent the upper edge of the rear wall l2. The main portion of the damper plate extends above this upper edgeof the rear wall, to close the hot gas passage H, but the damper plate has depending tabs 3| which extend downwardly, and which are shaped to fill the cold air passages C. The damper plate is swung by any convenient means, such as the arm 33 fast upon one of the trunnions 30. When swung into the dash line position of Figure 3, or with parts in the position shown in Figures 1 or 4, the main upper portion of the damper plate closes the hot gas passage H, and at the same time the tabs 3|, close the cold air passages C,

and the throat opening, made up of these several Y passages, is completely closed, except for the' usual clearances. However, when the damper plate is swung into the full line position of Figure 3, or into the position of parts'shown in Figure 2, the main upper portion of the damper plate swings to the rear, and the tabs 3|, being below the hinge axis, swing forwardly. While the passages H and C are simultaneously opened by this swinging, they still further segregate the currents in that the cold air, tending to spill or to blow downwardly through the passages C, is protected and directed rearwardly and downwardly by the overlying and forwardly swung tabs 3|, which are curved somewhat rearwardly, and is further protected by the rearwardly swung and more greatly elevated main portion of the damper plate. The upper part of the damper plate increases the depth of the pocket P' behind the damper frame, wherein the cold air tends to collect, to increase the capacity of that pocket, and the better to segregate the upflow and the downflow.

The segregation, then, is (a) by virtue of the different levels through which the opposed currents pass through the fireplace throat, (b) by reason of the segregation at different points in the width of the throat, and (c) by reason of the protection and segregation afforded by the damper plate itself.

In the closed position of the parts the cover 2 may conveniently rest upon the upper edge of the damper plate 3, as is seen in Figure 4, or upon the upper edge of the end walls I I. Since it is desirable to swing the cover 2 upwardly somewhat, so that the entire throat opening is not required to be accomplished by the rearward swinging of the more or less upright damper plate 3, it is convenient to operatively interconnect the damper plate 3 and the cover 2 so that the swinging of the damper plate effects corresponding upward swinging of the rear edge of the cover. Any convenient means to this end may be employed. As shown, a cam 4 is fast upon a trunnion 30, or may be formed as an integral part of the arm 33. This cam is so shaped that when the damper plate 3 is closed the cover 2 is permitted to rest upon the upper edge of the damper plate, but when the damper plate is swung towards open position, as in Figure 3, the cam, bearing beneath the cover 2, causes the latter to rise at its rear edge, and thus to open more widely the hot air passage H.

The damper shown in Figure 5 and 6 omits any separate or hingedly mounted cover or lid. The damper plate 39 is inclined more to the front, and the rear wall I2 is correspondingly more inclined than in the previously described form. The front wall I3 of the frame I is extended more to the rear, and the upper edge of the damper plate 39 rests against the upper edge of the front wall I3 when parts are in closed position. Also, when parts are in closed position the tabs 3| fill and close the passages C, as before. The damp-er plate swings, upon its trunnions 34, rearwardly towards open position, the tabs 3| swinging forwardly, into the throat opening. In this open position there are defined the segregated hot gas and cold air passages H and C, respectively, in substantially the same manner as previously described.

With the damper plate 33, in open position, more nearly horizontal than in the first form, a down blast might tend more strongly to swing it about its tilting axis. I prefer, therefore, to provide means to hold it in any set position, and to this end may employ such means as are disclosed in my Patent No. 1,500,154, dated July 8, 1924. Briefly, one or both of the trunnions 34 is formed with two or more spaced edges 35, parallel to and oifset from the pivot axis, resting, one or both, on the horizontal bearing surface l'l in the end wall N. If tilted so that one edge 35 only rests upon the surface I! the damper plate is in one extreme position-'for instancejin closed-position, as shown in Figure 6and if the other edge 35 only rests upon the surface I1, the damper plate is in the opposite extreme position. If both edges 35' rest upon the surface ILthe damper plate is balanced in an intermediate position. Additional means may be employed to prevent the damper plate from falling or being blown from any set position, such as the pin 38 upon the damper plate, capable of riding over the spaced stops 5 fixed to the adjacent end plate I I when the damper is manually swung, but capable of resisting swinging under the influence of drafts or blasts through the throat.

It has been suggested that the down-drafts occur principally or usually at the several corners of the flue, that they spread down the throat and enter the fireplace combustion chamber at the two ends of the throat opening. This is usually the case, and hence the cold air passage C are usually to be located at the two ends of the pocket P, with th hot gas passage H centrally disposed. Peculiar conditions may change this, however, and to meet such conditions it is understood that the hot gas and the cold air passages may be differently located, without departing,

from the spirit of my invention.

The damper plate has been described as an upright one, complemental to the rear wall of the frame, but it will be understood that it may be otherwise positioned, arranged, and related, and still accomplish equivalent results in a similar manner. If the movable cover is omitted, as in Figures 5 and 6, the damper plate may, in part, take the place thereof. Likewise, instead of being hinged, the damper plate may be otherwise movable, or if hinged, the hinge axis may be otherwise located. Indeed, in the achievement of certain advantages, no damper plate is needed. The basic principle of this invention is the segregation, resulting from natural gravity or thermal causes, of the upflow and downflow, and various 7 changes in the form, character, and arrangement of the elements of a fireplace structure or of a damper will suggest themselves as suitable to accomplish these results in an equivalent way.

What I claim as my invention is:

1. A fireplace damper comprising, in combination, a frame defining a throat opening, and incorporating an upstanding bafile at the rear of the opening, terminating short of at least one end of the opening to leave, between its end and the adjacent end of the frame, a low-lying cold air passage, and a damper plate complementally shaped to close the cold air passage and the remainder of the opening, including the hot gas passage over said baffle, and means guiding said damper plate for movement to simultaneously open or close said passages.

2. A fireplace damper comprising, in combination, a frame defining a throat opening, and incorporating an upstanding bafiie at the rear of the opening, which terminates short of atleast one end of the frame, to leave, between its end and the adjacent end of the frame, a low-lying cold air passage, an upright damper plate over lying the baffle, and complementally shaped to close the throat opening, including the low-lying cold air passage, and hinge means mounting the damper plate to swing upon a transverse axis adjacent the upper edge of the baffle, to open simultaneously and to separate the cold air passage and a hot ga passage over the top of the damper plate.

3. Afireplace damper comprising, in combination, a frame having end walls, a front wall, a covenand a rear wall upstanding less than the height of the rear edges ;of the end walls, to leave a hot gas passage between itself and the top, and termi-nating'short of the end walls, to leave low-lyingcold air passages between'itself and the end walls, a damper plate hingedly mounted in the frame upon a substantially horizontal'axis adjacent the upper edge of the rear wall, said damper plate being shaped, above its hinge axis, to close the hot gas passage, and having tabs depending below its hinge axis, positioned and shaped to close the cold air 'pas- Sages'and means to swing the damper plate from such closed position to an open position, wherein its upper portion is swung rearwardly to open the hot gas passage over its upper edge, and its tabs are swung forwardly to open the cold air passages, and toseparate the downflowing cold air from the upfiowing hot gas.

4. A fireplace damper comprising, in combination, a frame having end walls, a front wall, a cover, and a rear wall upstanding less than the height of the rear-edges of the end walls, to leave a hot gas passage between itself and the top, and terminating short of the end walls, to leave low-lying cold air passages between itself and the end walls, a damper plate hingedly V zontal axis adjacent the upper edge of the rear wall, said damper plate being shaped, above its hinge axis, to close the hot gas passage, and having tabs depending below its hinge axis, positioned, and shaped to close the cold air passages, and means to swingthe damper plate from such closed position to an open position, wherein its upper portion is swung rearwardly to open the hot gas passage over its upper edge; and its tabs are swung forwardly to open the cold air pas sages, and to separatethe 'downfiowing cold air from the upfiowing hot gas, means'hingedly mounting the cover upon a transverse axis adja-, cent the front wall of the frame for upward swinging of the covers rearedge, and meansfor so swinging the cover, simultaneously with opening movement of the damper plate t'o increase the area of the hot gas passage,

5. A fireplace damper comprising, in combination; a frame having end walls, a front wall and a rear wall upstanding to a height less than theheight of the rear edges of the end walls, to leave a hot gas passage'above the rear wall, and terminating, at one end at least, short of the end wall, to define a low-lying cold air passage, a cover hingedly mounted in the frame along a transverse axis adjacent the upper edge of the front wall, to close the top of the frame, a damper plate shaped to close the opening between the rear wall and the cover, including the hot gas passage and the cold air passage, and mounted in the frame for movement between such closed position and a position wherein both passages are open, and means inte-rengageable between the damper plate and the cover, to raise the latter,

to increase the area of the hot air opening, as

the damper moves towards its open position.

6. A fireplace damper comprising, in combination, a frame defining a throat opening, a bafiie spaced at its ends from the ends of the throat opening, but in part closing the interme diate portion of such opening, and a damper late of a shape and so mounted as to cooperate with the frame'and the bafiie to close the throat opening, and guided 'IOI movement "to open such openingythereby to leave flow-lying end passages for down-flowing cold air and a passage over the baflie for upflowing hot gas.

7. A fireplace damper comprising, in combination, a frame defining a throat opening, an upstanding baflle spaced at one end, at least, from the end of the throat opening, to define a lowlying passage for cold air around the end of the baffle, and a passage for hot gas over the upper edge of the bafile, and damper means guided for movement relative to the frame, between a 10 closed position, wherein communication is substantially cut off between the combustion chamber below and the fiue above the throat opening, and an open position, wherein the two passages 8. A fireplace structure defining a throat affording communication between the combustion chamber below and the flue above, through which throat, in the portion intermediate its ends, the hot gases normally flow upwardly, said fireplace structure being likewise formed and arranged to define a cold-air pocket at a level below the throat but communicating freely and directly at all times with the fiue, and to define a passage opening from the lower part of said pocket, adjacent an end of the throat and out of the line of normal updraft, and leading to the combustion chamber, to segregate downfiowing cold air from upflowing hot gas, and means movable to reguare open for passage of segregated, transversely 15 late such downflow.

spaced currents, to avoid interference therebetween.

ALBERT P. ROBINSON. 

